Conventionally, in this type of positioner an automatic setup has been performed product, prior to actually controlling the valve opening of the regulator valve, after installation in the workplace (either new insulation or as a replacement), to adjust automatically the zeroing and the span, and to tune the control parameters. Note that the zero and span adjustment and the tuning of the control parameters is performed also during scheduled maintenance as well.
As part of this automatic setup, there is a procedure for executing full opening/closing strokes of the valve in order to tune the control parameters, where the average response time TRES, for the valve to traverse between the 10% position and the 90% position of the valve during the full opening/closing strokes of the valve is measured, to determine the size of the operating device from the average response time TRES, to determine the control parameters from the operating device size that has been determined and from the hysteresis level of the operating device. See, for example, Japanese Patent No. 3511458 (“the JP '458”) Japanese Unexamined Patent Application Publication No H11-166655).
The conventional process for finding the average response time TRES will be explained using the flowchart presented in FIG. 9.
(1) The driving signal (the control input) IM when converting the inputted electric signal into an air pressure is set to IMMIN (the minimum) (Step S101). This causes the valve to move toward the fully closed position (the 0% position), as illustrated in FIG. 10. Note that while there is also a type wherein the valve moves towards the fully open position (the 100% position) when the driving signal IM is set to IMMIN, the explanation here will be for those that moved toward the fully closed position.
(2) Thereafter, upon detection that the movement of the valve has stopped and settled (YES in Step S102), the valve opening position A at that time is stored (Step S103).
(3) Following this, the driving signal IM is set to IMMAX (the maximum) (Step S104). Doing this causes the valve to move toward the fully open position (a full opening operation). (4) Thereafter, upon detection that the movement of the valve has stopped and settled (YES in Step S105), the valve opening position B at that time is stored (Step S106).
(5) Following this, the driving signal IM is set to IMMIN (Step S107). This causes the valve to move to the valve opening position A from the valve opening position B (a full closing operation).
(6) During this interval, the valve open position is monitored and the time is measured, to measure and store, as the first response time Tdown, the time for the opening of the valve to arrive at the 10% position, from the 90% position, of the interval between the valve opening positions A and B (Step S108).
(7) After arriving at the valve opening position A, the driving signal IM is set to IMMAX (Step S109). This causes the valve to move toward the valve opening position B from the valve opening position A (t full opening operation).
(8) During this interval, the valve open position is monitored and the time is measured, to measure and store, as the second response time Tup, the time for the opening of the valve to arrive at the 10% position, from the 90% position, of the interval between the valve opening positions A and B (Step S110).
(9) Following this, the average of the first response time Tdown, measured in Step S108, and the second response time Tup, measured in Step S110, is taken to calculate the average response time TRES (where TRES=(Tdown+Tup)/2) between the 10% position and the 90% position for the valve (Step S111).
Averaging, in this case, Tdown and Tup is because there are times wherein Tdown does not equal Tup. That is, sometimes there is a difference in the speeds in the operating device for the direction of increasing the valve opening and the direction of decreasing the valve opening, so that taking an average of the two enables better precision.
However, in the conventional procedure, set forth above, for finding the average response time TRES, operations for moving the valve all the way from end to end (full stroke operation cycles) are performed three times (in Steps (3), (5), and (7)), and thus there is a problem in that finding the average response time TRES is extremely time-consuming.
The majority of the time required in the automatic setup of the positioner as a whole is occupied by the full stroke operation cycles for the valve, so a reduction in the number of full stroke operation cycles reduces the amount of time required in the automatic setup.
Note that when, in Step (1) the driving signal IM is set to IMMAX, the process diagram that shows the change in the valve opening position for the valve illustrated in FIG. 10 can be replaced by a process diagram as illustrated in FIG. 11. FIG. 7, shown in the JP '458, is no more than that which is shown beginning with Step (5) in the process diagram presented in FIG. 11. That is, the operation in FIG. 7, illustrated in the JP '458, assumes that the valve opening positions A and B for the valve have been found prior to entering into this operation.
The present invention is to solve such a problem, and an aspect thereof is to provide a positioner wherein the time required for the automatic setup can be reduced.